Various methods of manufacturing fasteners, such as, for example, pierce nuts and the like have been used in the past and have provided satisfactory results enabling production of these types of fasteners in high volumes. End users of these pierce nuts have preferred using a continuous strip of pierce nuts connected side to side with a wire such as is disclosed in U.S. Pat. No. 3,845,860, for Fastener Strip.
The installation of the pierce nuts is greatly simplified when provided to an end user in a continuous strip wound in a coil, which eliminates the need for expensive bowl mixers and alignment devices used to align these fasteners prior to production installation into a panel. A common process for providing coils of nuts attached in a strip, such as described above, includes a combination of batch and inline process which is presently utilized.
For example, a coil of steel rod is provided to a nut manufacturing facility, and is preferably, formed to provide a cross-sectional geometric shape necessary to pierce, and/or clinch, sheet metal, and to provide a groove to receive the wire in a manner set forth above. This rod is processed through a die that both cuts individual pierce nuts and pierces an aperture through the rod forming an inner annular surface in each individual fastener. A tapping machine is positioned subsequent to the die press to provide a helical rib around the inner annular wall of the pierced aperture of each pierce fastener. These fasteners are subsequently placed into a bulk bowl feeder that aligns a plurality of the fasteners in an orientation necessary for continued processing. Various problems are associated with the above-mentioned process. For example, during the cutting stage of the die press, various grooves, and more specifically, the groove designated to receive the attachment wire is known to be deformed making it difficult to insert the wire into the wire groove in a uniform manner. Furthermore, defects associated with location and dimension of the nut apertures and vehicle groove have not yet been identified.
Once the nuts have been oriented in a uniform fashion, the nuts are transferred via a track to a wire insertion and knurling operation to attach the nuts in a continuous strip. A second press or an equivalent roller inserts the wire into the aligned wire groove of each nut and a knurling machine deforms the nut over the wire for retaining the wire in the aligned groove thereby forming the continuous strip of fasteners. Subsequently, the fasteners are rolled in a coil for shipment and for use at a production facility that installs pierce fasteners as is known to those of skill in the art.
A further problem associated with the prior art method is realized when an error occurs during the tapping or piercing process resulting in the defective formation of the aperture or helical rib disposed upon the inner surface of the aperture. Once the fasteners have been attached in a strip, it is impossible to replace a defective fastener without breaking the continuous strip resulting in a partial coil of fasteners that is undesirable to the end user. Therefore, a nearly full coil of fasteners is frequently viewed by the end user as being undesirable when a single defective fastener is discovered after the fasteners have been attached in a continuous strip. Furthermore, the smaller strip of fasteners that are separated from the nearly full coil of fasteners is generally scrapped.
A still further problem exists with the present state of the art relating back processing that reduces the throughput of fasteners through the manufacturing process. It is known to those of skill in the art that orienting nuts in a bowl feeder is a bottleneck in the manufacturing process that reduces the rate at which fasteners are manufactured resulting in a more expensive fastener. It would be desirable to eliminate the bowl feeder from the manufacturing process. Furthermore, it would be desirable to provide a continuous manufacturing process that solves the problems associated with the prior art method of manufacturing by eliminating defective nuts found in a continuous strip, eliminate the batch process of manufacturing, and providing a consistent, continuous groove formed by adjacent nuts in a strip.